net/quic/quic_sent_entropy_manager.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 //
   5 // Manages the packet entropy calculation for both sent and received packets
   6 // for a connection.
   7
   8 #ifndef NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_
   9 #define NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_
  10
  11 #include <deque>
  12
  13 #include "net/base/linked_hash_map.h"
  14 #include "net/quic/quic_framer.h"
  15 #include "net/quic/quic_protocol.h"
  16
  17 namespace net {
  18
  19 namespace test {
  20 class QuicConnectionPeer;
  21 }  // namespace test
  22
  23 // Records all sent packets by a connection to track the cumulative entropy of
  24 // sent packets.  It is used by the connection to validate an ack
  25 // frame sent by the peer as a preventive measure against the optimistic ack
  26 // attack.
  27 class NET_EXPORT_PRIVATE QuicSentEntropyManager {
  28  public:
  29   QuicSentEntropyManager();
  30   virtual ~QuicSentEntropyManager();
  31
  32   // Record |entropy_hash| for sent packet corresponding to |packet_number|.
  33   void RecordPacketEntropyHash(QuicPacketNumber packet_number,
  34                                QuicPacketEntropyHash entropy_hash);
  35
  36   // Retrieves the cumulative entropy up to |packet_number|.
  37   // Must always be called with a monotonically increasing |packet_number|.
  38   QuicPacketEntropyHash GetCumulativeEntropy(QuicPacketNumber packet_number);
  39
  40   // Returns true if |entropy_hash| matches the expected sent entropy hash
  41   // up to |largest_observed| removing packet numbers from |missing_packets|.
  42   // Must always be called with a monotonically increasing |largest_observed|.
  43   bool IsValidEntropy(QuicPacketNumber largest_observed,
  44                       const PacketNumberSet& missing_packets,
  45                       QuicPacketEntropyHash entropy_hash);
  46
  47   // Removes unnecessary entries before |packet_number|.
  48   void ClearEntropyBefore(QuicPacketNumber packet_number);
  49
  50  private:
  51   friend class test::QuicConnectionPeer;
  52
  53   typedef std::deque<QuicPacketEntropyHash> SentEntropyMap;
  54
  55   struct CumulativeEntropy {
  56     CumulativeEntropy() : packet_number(0), entropy(0) {}
  57
  58     QuicPacketNumber packet_number;
  59     QuicPacketEntropyHash entropy;
  60   };
  61
  62   // Convenience methods to get the largest and smallest packets with entropies.
  63   QuicPacketNumber GetLargestPacketWithEntropy() const;
  64   QuicPacketNumber GetSmallestPacketWithEntropy() const;
  65   // Convenience method to get the entropy hash for |packet_number|.
  66   QuicPacketEntropyHash GetPacketEntropy(QuicPacketNumber packet_number) const;
  67
  68   // Update the cumulative entropy to |packet_number|.
  69   void UpdateCumulativeEntropy(QuicPacketNumber packet_number,
  70                                CumulativeEntropy* cumulative) const;
  71
  72   // Maps packet numbers to the sent entropy hash for the packet number.
  73   SentEntropyMap packets_entropy_;
  74   QuicPacketNumber map_offset_;
  75
  76   // Cache the cumulative entropy for IsValidEntropy.
  77   CumulativeEntropy last_valid_entropy_;
  78
  79   // Cache the cumulative entropy for the packet number used by EntropyHash.
  80   CumulativeEntropy last_cumulative_entropy_;
  81
  82   DISALLOW_COPY_AND_ASSIGN(QuicSentEntropyManager);
  83 };
  84
  85 }  // namespace net
  86
  87 #endif  // NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_